How To Waterproof Your Shed

As the wet months draw closer, you’ll want to make sure that your house and garden are prepared for the rain. Water can play havoc if it gets inside, and this is true for both your house and your shed.

Sheds can often be left to suffer over winter, but there’s no need to abandon them when the rain falls. Waterproofing your shed is a simple process and it will ensure that no damage comes to the building or what’s inside.


If you’re not sure how to waterproof a shed, or simply wondering what the best waterproof shed treatment is, then we’ve got you covered. This blog will give you all the information you need to make your shed waterproof.


Read on to find out how!

Dealing with “Water Ingress”

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Waterproofing your garden shed is simpler than it might seem. When water gets inside a structure, it is called water ingress. Simply put, you need to make sure that there is no way that water can get inside – you need to remove all points of water ingress.

This might sound a bit complicated at first, but after reading this guide you’ll realise how easy it is to do.

If you have a metal shed or a plastic shed, don’t ignore this guide. While the materials used for these buildings are themselves usually waterproof, it doesn’t mean that water ingress won’t cause damage to the structure. For example, allowing water inside can lead to condensation which speeds up the rusting process in metal.

To waterproof your shed securely, there are a number of stages to go through and things to look out for. This blog will explain them all, step by step. Let’s get started!

Inspect the Structure

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The first thing to do is inspect your shed completely. Before doing any work, you need to find out how waterproof it already is. Conduct a thorough inspection of the structure, looking for any obvious places where water might be collecting.

Below is a handy checklist of places to search and what to look out for:

  • Check the roof for leaks. This is the place where water ingress happens the most and with the greatest effect.
  • Check the walls, doors, and windows for significant holes, cracks, or signs of rot. You should also check if the windows come away from their frames, or if the framing has gaps or is broken.
  • If your shed has a gutter, do a full inspection of the gutters and drains for holes or a build-up of rubbish.
  • Check where the shed meets the floor. There could be gaps between the wall and the floor or base, as these are areas where water can easily seep in.

If you find a hole or a place where water could ingress, then keep it in mind. Cover it there if you can, but it is always good to reinforce any fixes with proper materials or seals later.

Once you’ve checked everything over, you should have a good idea of the areas your shed is lacking in and what you’ll need to focus on to fix them. But be careful – even if you’ve inspected everything there are holes that might you may have missed. Just because you can’t see a gap doesn’t mean it isn’t there!

Now you have an idea of what needs to be fixed – let’s move on to solving the issues.

Secure The Foundations

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It is a good idea to work from the bottom up when waterproofing your shed. This means starting with the foundations.


There are two ways to waterproof the base of your shed. You can either raise your shed off the ground using a raised base or lay a waterproof membrane underneath. Both of these will stop moisture from permeating through the bottom of the structure.

The option you choose will likely depend on the material your shed sits on and your budget – although you can use both together for additional safety. Let’s run through both.

Using a raised base

BillyOh Wooden Shed Premium Tongue and Groove Floor
BillyOh Wooden Shed Premium Tongue and Groove Floor

Using a base lifts the whole shed off the ground. This makes it clear of any ground or surface water that might accumulate around the base. It also provides a sturdy foundation for the building to sit on.

While shed bases are usually more expensive than membranes, they can be placed on any flat patch of ground.


Installing a membrane

A waterproof membrane is fitted underneath the shed and the surface it sits upon. The membrane is breathable, meaning it won’t hold water and become soggy, but it won’t let water pass through either.

All you need to do to install the membrane is place it between the shed and the base it sits upon. However, the shed will already need to be sitting on a solid surface such as concrete – or a raised base. If you don’t have one of these in your garden, it might be easier to use a raised base.

Either option is sensible and effective at waterproofing the bottom of your shed – choose the option that suits you and your situation best.

Walls, Windows And Doors

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Next, it’s time to seal up the shed’s walls and fittings. Wooden material shrinks over time, causing cracks and gaps to open up in the structure. If you saw any in your initial inspection, now is the time to come back and clean them up properly.

Seal from the inside first. For gaps in the wood, you’ll want to fill them up with silicone caulk. Caulking is a quick and effective way to block up holes, and most importantly it is easy to do.


If this is your first time caulking, it’s always a good idea to look through a quick guide on the process.

Caulk all the cracks you can find, paying special attention to the edges of the shed where two walls meet – it is very common for small gaps to appear there. You should also caulk around the windows if there are gaps in the frame.

On the outside of the shed, find any parts where the wood is decaying or wasting away. Take out the rotten wood with a screwdriver or tool and fill the void with wood filler. After all the gaps are filled and caulked, apply a layer of wood preservative to all of the outside walls and doors. This will keep the wood in good condition for longer.

The Roof

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Waterproofing your shed roof is arguably the most important part of the whole process. Water ingress happens most often on the roof, as it comes into contact with water the most.

First of all, you wanted a shed with a slanted or apex roof, which allows water to run off easily. A flat roof will allow water to collect, so it is highly recommended not to buy a flat-roofed shed. 

Shed roofing should always be covered by roofing felt. Felt is a lightweight, waterproof roofing material that is fitted over the top of the shed roof for protection from rain and the other elements.

There are some great guides out there that can help you out if you’re not sure how to waterproof your shed roof with felt. But we’ve got you covered here too – simply follow the brief instructions below:

  • If you already have felt on your shed roofing, carefully remove it and take away any dirt build up with it. It is best to do this when it is dry outside.
  • Measure the dimensions of where your roofing felt will go, taking into account any overhang that your shed has.
  • Cut the felt to size, and lay it over the shed to check sizing. Make any adjustments, then cover the back of the felt with bitumen paste. Bitumen will stick the felt to the roof without using nails which create holes for water to seep in through.
  • Stick the felt to the roof and smooth it down as much as possible. Any gaps or creases will allow water to accumulate.

A well-fitted covering of roof felt can protect your shed from water ingress for years, but remember to keep checking for holes or leaks. If you want a more in-depth guide, check out our step-by-step helper here.

With this step complete, your shed should be completely resistant to water.

But that doesn’t mean you can’t go that extra mile to keep it water-free!

Extra Steps

Someone painting wooden slats with waterproof paint
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There are plenty of other measures you can put in place if you want to super-proof your shed. While these aren’t essential in all cases, they will make a difference over time.

If you find that your shed keeps getting wet no matter how hard you try, these may just help you solve the problem. Let’s take a look.

Waterproof paint

While a layer of wooden preservative should be enough to protect the wood from water, waterproof paint gives it extra protection. Wood treatments such as paint can really save the day when it comes to prolonging the life of your garden shed.

Waterproof shed paint resists water completely, so the wood underneath does not absorb moisture or become damp. A couple of coats of waterproof paint will repel water before it even gets a chance to come inside.

Install ventilation

Vents and openings may not seem like the obvious solution, but they do the important job of letting out damp and moist air. Moisture in the air is just as dangerous as water itself, so it’s important to ventilate if possible.

Install windows that can be fixed open, a ventilation hatch, or a pair of openable roof vents to allow air circulation. All of these are good ways to keep your shed fully waterproof.

Bringing It All Together

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Despite what it might seem, waterproofing your shed is not difficult or complicated.

All you need to do is follow the simple steps above, then spend a bit of time checking back in the weeks after to make sure everything is working as intended. With any luck, you should now have a completely waterproof shed!

Let’s just run back over those steps again:

  • Start by inspecting your shed all over, checking for gaps, holes – find anywhere that water could be getting in.
  • Seal up the foundations of your shed by raising it off the ground or installing a breathable water membrane underneath the building. Alternatively, do both!
  • Waterproof all walls, windows, and doors. Use silicone caulk to fill any gaps, and apply wooden preservative to the exterior.
  • Cover the roof by installing waterproof felt using our quick and easy guide.
  • Go the extra mile by adding additional ventilation or using waterproof paint.

Once you’ve completed all those steps, you’ll never have to worry about water in your shed again!

If you’re interested in buying some of our shed waterproofing products, shop using the button below! Or click here to explore our selection of shed paints.

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Still stuck? We’ve answered a few of your most-asked questions below!

While painting the inside of your shed is a personal choice, it is a good idea to apply a layer of wood preservative to the inside if you get the chance. This will help give the wood an extra layer of durability. If you do paint the inside, using waterproof paint will help to reinforce the wood from any water ingress or moist air.

Insulating your shed can help waterproof the structure by placing extra layers between water and the inside of the shed. Insulation also helps control airflow and heat within the building, useful for keeping out cold, moist air. If you’re interested in insulating your shed, check out our guide here!

Waterproofing is important for retaining the longevity of your garden shed, and for protecting everything you keep inside. Water ingress can cause major damage to the structure by rotting the wood, sometimes damaging it beyond repair. Waterproofing helps keep the building and whatever you use it for safer for longer.